How to calculate the equivalent resistance using wye delta ?

1. The problem statement, all variables and given/known data
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We need to find the equivalent resistance along A to B ie AB2. Relevant equations
R=(1/R1 + 1/R2+.........+1/Rn)^-1 , Y-Delta transformation , equation for parallel combination, equation for series combination.3. The attempt at a solution
I tried wye-delta but my teacher says that I need not use wye-delta .How possible? I have two answer 1.43 ohms and 1.6 ohms .What is the actual equivalent resistance? Can you please solve these problems?

Well, I believe wye-delta will give you the answer since there are a lot of wyes and deltas in the circuit, but I think there is other way(simpler, maybe). Consider the two 2Ω resistors in the middle, which are parallel to AB. Replace each of them by a parallel combination of two 4Ω resistors. Now cut the circuit into two halves along the horizontal symmetry, separating the 4Ω resistors.

Well, I believe wye-delta will give you the answer since there are a lot of wyes and deltas in the circuit, but I think there is other way(simpler, maybe). Consider the two 2Ω resistors in the middle, which are parallel to AB. Replace each of them by a parallel combination of two 4Ω resistors. Now cut the circuit into two halves along the horizontal symmetry, separating the 4Ω resistors.

Lets call the side along which we cut the circuit as CD Now, the equivalent resistance( between A and B )of the lower part and equivalent resistance of the upper part(between C and D) will be in parallel, which will give you net resistance between A and B. Out of that, equivalent resistance of the lower part is very easy to find, just by series-parallel combination. But for the upper part, I think you need to use wye-delta at least once(or twice). Seems that you can't get rid of wye-delta so easily! But I think the no of wye-delta conversions is reduced this way.

Well I'm afraid telling the final answer is not allowed here and if I did so, it will be removed immediately and I'll be warned! It will be helpful if you drew and posted the diagrams here. What answer have they provided? I just want to verify if my approach is right. Otherwise, it will waste your precious time.

Nope, this approach is not right. We are calculating the resistance between A and B. So, lower part resistance will be between A and B but upper resistance will be between C and D. They are not in parallel. I ran a quick simulation on my phone and verified it. That was a silly mistake! But I think there should be some other method since the configuration is symmetric. I'll try to work it out!

Well I'm afraid telling the final answer is not allowed here and if I did so, it will be removed immediately and I'll be warned! It will be helpful if you drew and posted the diagrams here. What answer have they provided? I just want to verify if my approach is right. Otherwise, it will waste your precious time.